Grid manufacturing process



c. A. WHITELEY 2,896,307

GRID MANUFACTURING PROCESS July as, 1 59' 2 Sheet s-Sh et 1 Filed May14, 1954 L1 U L Ll l I I H 29v T 28 INVENTOR I Cf/AALEZSA. H/TELEY BY IZ 1:96:

ATTORNEY a MANUFAcrG PROCESS Charles A. Whiteley, East Meadow, N.Y.,assignorto The Sperry Rand Corporation, a corporation of Dela- WareApplication May '14, 1954, Serial No. 429,807 4 Claims. (Cl. 29-25. 14)

The present invention relates to a process of manufacturing grids foruse in electron beam tubes such as klystrons, travelling wave tubes andhigh frequency triodes.

One of the most reliable and efficient kinds of grids prominently usedin electron beam tubes is comprised of spaced, cantilever-type vanesmounted upon an annular supporting member and projecting inwardlythereof. The individual vanes of some grids of this type are free fromeach other at their inner ends within the supporting member. In othergrids of this type the vanes of certain pairs of vanes are joinedtogether at their inner ends so that the aforesaid pairs are eachcomprised of an integral element bent into a desired configurationsimilar to a V, for example.

Yet another type of grid which has been used in klystron tubes, forexample, is comprised of a plurality of spaced vanes extending acrossthe interior of an annular grid supporting member. The vanes are alfixedto the inner surface of the aforesaid member at opposite regions thereonwith the front and back edges of the vanes being coplanar, respectively.

The vane elements of most grids of the aforedescribed types are formedfrom thin strip sections of metal. Each section must be of predeterminedlength and sharply bent at one or more places to form one or more vaneelements and integral supporting portions therefor. The supportingportions are made to conform to the inner surface of the annular gridsupporting member and are soldered or brazed, for example, to theaforesaid surface.

Heretofore it has been difficult to form grids of the aforedescribedtypes. Accurate bends are required to be made in the metallic stripsections so that a rugged assembly having a predetermined distributionof grid elements can be produced. Generally such bends have been madewhile the metallic strip sections are at room temperature, acold-bending process, and it has been time-consuming and expensive tomake the bends with the required precision to provide an accurate andrugged grid assembly. Furthermore, since sharp bends are generallyrequired, the cold-bending process may result in a grid having elementswhich are unduly weak and fragile at the bends.

It is an object of the present invention to provide an improved processof manufacturing grids for use in electron beam tubes.

It is a further object to provide a process of manufacturing vane typegrids which is less time-consuming and less expensive than processesheretofore known in the art.

It is still another object of the present invention to provide a processas aforedescribed for accurately manufacturing vane-type grids of morerugged construction than similar grids of the same type and sizeheretofore known in the art.

The foregoing objects are attained by a process which includes the stepsof: interwinding an elongated metallic element back and forth acrossparts of the face of a jig from one to another of a plurality ofpredeterminedly shaped and distributed protuberances extending fromsaidjig face; heating the assembly comprising said jig and said element to apredetermined temperature and tightening said element about saidprotuberances so that por tions of said element are heat-bent andclosely conformed to parts of said protuberances; and cooling saidassembly to thereby permanently fix the shapes of the bends in saidelement and provide a rigid and accurate configuration suitable for agrid in an electron beam tube device. 7 g

If the jig has an appreciably higher temperature coefiicient ofexpansion than that of the grid element the tightening part of theprocess can be efliected by heat expansion during the heating step,provided the ends of the grid element are anchored.

Furthermore, if at least some of the jig protuberances are in a ringaround the axis of the jig and have outer-5 most parts conformal to anannulus, an annular grid supporting member can be readily bonded toportions of the grid element which are interwound therearound. If thesupporting member has: a slightly lower temperature coeificient ofexpansion than that of the jig, the heating step will cause the jig toexpand and the aforementioned grid element portions to be compressedagainst and more closely conformed to the inner surface of the annularsupporting member. The bonding is achieved by providing suitable brazingmeans having a melting point lower than that to which the assembly isheated between the inner surface of said supporting member and theaforesaid grid element portions.

The foregoing process and all of the objects and advantages of thepresent invention will become more apparent to those skilled in the artfrom the following detailed description of the invention taken inconnection with the accompanying drawings in which:

Figs. 1, 2 and 3 are perspective views of three different types of gridswhich can be manufactured in accordance with the process of the presentinvention;

Fig. 4 is a plan view of a jigfror forming the grid shown in Fig. 1;

Fig. 5 is a side view of the jig shown in Fig. 4;

Fig. 6 is an exploded view in perspective illustrating theaforementioned jig, a grid element interwound thereon and ring membersutilized in the grid forming process;

Fig. 7 is an enlarged sectional view of the jig and interwound gridelement of Fig. 6, and shows the position of the ring members shown inFig. 6 at an intermediate stage in the grid forming process;

Fig. 8 is a sectional view of'the jig and interwound element similar tothat shown in Fig. 7, and shows the position of the ring members shownin Figs. 6 and 7 at a further stage in the grid forming process;

Fig. 9 is a plan View of a further jig for forming the grid shown inFig. 3; and r Fig. 10 is a side view, shown in Fig. 9.

A first grid assembly manufactured in accordance with the process of thepresent invention is shown in Fig. 1. This assembly is comprised of athin metallic element 11 which is bent to form a plurality of V-shapedsections 12, supporting portions 13 and V-shaped sections 14symmetrically disposed about an axis of an annular metallic supportingmember 16. The supporting portions 13 are rigidly fixed to or mountedupon the inner surface of member 16. The vertexes of V-shaped sections12 are located inward of member 16 by equal distances along alternateones of equally spaced radii of member 16. The vertexes of V-shapedsections 14 are located further inward of member 16 by equal distancesalong other alternate ones of the aforementioned equally spaced radii ofmember 16.

partly in section, of the jig The grid assembly shown in Fig. 1 is ofthe cantilever type since there is no support-of the arms or vanes ofthe V-shaped sectionsrlz and 14at their inner ends within the gridSupporting member 16. Since certain pairs of arms are joined together attheir inner ends to form the V- shaped sections 12 and 14, the gridshown in Fig. 1 is usually designated as a pyramid-type grid. d V

A' modification of the pyramid-type grid illustrated in Fig. l is shownin Fig. 2. In the latter figure the grid is comprised of a plurality ofJ-shaped metallic sections 17 rigidly mounted and symmetrically disposedupon the inner surface of an annular, metallic supporting member 18.Bent portions 19 of sections 17 are utilized to rigidly support eachsection upon member 18. The adjacent sections 17 of the cantilever typegrid assembly shown in Fig. 2 are mirror images of each other.Therefore, this assembly could be readily formed from the structureshown in Fig. 1 merely by cutting or shearing the V- shaped sectionsthereof at their apexes. Yet another type of grid assembly which can bemanufactured in accordance with the process of the present invention isillustrated in Fig. 3. This assembly is comprised of a thin metallicelement 21 formed into a plurality of curved vane sections 22 andsupporting portions 23. The supporting portions 23 are rigidly mountedupon the inner surface of an annular, metallic supporting member 24. Auniform spacing is-provided between the vane sections 22 with the narrowfront and back vane edges being coplanar, respectively. The gridassembly shown in Fig. 3 is known in the art as an arched-vane grid. Thevane sections 22 are curved so that changes in temperature to which thegrid may be subjected will not cause the front and back edges thereof todeviate from their original planes.

Referring to Figs. 4 and 5, a cylindrical mandrel or jig 26 is providedfor forming the grid assembly shown in Fig. 1. The jig 26 is comprisedof a bottom cylindrical section 27, an upper coaxial cylindrical section28 having a smaller diameter than section 27, a flat, annular jig seat29 outward of section 28 at the top of section 27, and a plurality ofspaced protuberances 31, 32 and 33 extending from a flat upper face 30of jig section 28.

The sides of protuberances 31, 32 and 33 are perpendicular to the face30 of section 28. Each protuberance has the same thickness along theaxis II through the center of jig 26. This thickness should generally beas large as the width of the metallic element 11 shown in Fig. 1.

The protuberances 31 are all of the same size and shape. Six of theseprotuberances 31 are symmetrically disposed in a ring concentric withthe aforementioned axis II of jig 26 as shown in Fig. 4. The innermostends of protuberances 31 nearest the axis II of jig 26 are spaced fromthe axis of jig 26 by equal distances determined by how far inward it isdesired for the V-shaped elements 14 of Fig. 1 to project. Theseinnermost ends stantially aligned with a side of an adjacentprotuberance 31, the other side of each protuberance 33 being alignedwith a side of an adjacent protuberance 32. The outermost parts or endsof protuberances 33 farthest from axis II of jig 26 are conformal withthe cylindrical side of the section 23 of jig. 26.

One of the protuberances 33 is divided in half to provide a slot 34through the middle thereof. The width of the slot 34 is made slightlylarger than twice the thickness of the metallic element 11. This is doneso that end portions 36 and 37 of element 11 can be anchored in slot 34during the grid forming process.

The dot-dash lines back and forth across parts of the face 30 of jig 26in Fig. 4 illustrate generally the positions that V-shaped elements 12and 14 and portions 13 of the grid shown in Fig. 1 would assume if thisfinished grid were seated upon the face 30 of jig section 28 to envelopthe jig protuberances. It can readily be seen, therefore, that theparticular sizes, shapes and locations of protuberances 31, 32 and 33are specifically determined in accordance with particular configurationof the grid to be formed.

The jig 26 shown in Fig. 4 is composed of metal having a relatively hightemperature coefiicient of expansion compared with the temperaturecoefiicient of expansion of the metal of grid element 11. The jig 26including its protuberances 31, 32 and 33 is formed by machining,casting or any other conventional jig forming process known in the art.

Referring to Fig. 6, the element 11 shown interwound upon jig 26 isoriginally in the form of a flat strip of metal having a greater widththan thickness. A first end portion 36 of the metallic strip is insertededgewise into the slot 34 of one of the protuberances 33 of the jig 26to begin the grid forming process. The strip is then bent in a clockwisedirection around one half of the outermost part of this protuberance 33,drawn toward the axis II of jig 26 across part of its face along thealigned sides of the aforesaid element 33 and the most adjacent element32, bent around the innermost curved end of this protuberance 32, anddrawn back along the aligned sides of the aforesaid element 32 and thenext protuberance 33 displaced in a clockwise direction from theprotuberance 33 containing the slot 34. This procedure is continueduntil the metallic element 11 is interwound back and forth around theoutermost end part of each protuberance 33 and the innermost end part ofeach protuberance 32 and the innermost end part of each protuberance 31.One narrow edge of element 11 is maintained in abutment with the face 30of section 23of the jig 26, the opposite narrow edge thereof beingcoplanar with the tops of pro- I ttuberances 31, 32 and 33.

are located at positions corresponding to the apexes of theaforementioned V-shaped sections 14.

.The protuberances 32 are also of the same size and shape, though havinga different size and shape than the protuberances 31. Six protuberances32 are symmetrically interposed between the six protuberances 31,respectively. The innermost ends of protuberances 32 nearest the axis IIof jig 26 are spaced from the aforesaid axis by equal distancesdetermined by how far inward it is desired for the V-shaped elements 12in Fig. 1 to project, these ends being located at positionscorresponding to the apexes of the aforementioned V-shaped sections 1 2.

:The protuberances 33 are also of the same size and shape, and aresymmetrically disposed in a ring concentnc with protuberances 31 and 32.Twelve protuberances 33 are provided in the particular jig constructionillustrated. Each of protuberances 33 is arranged to be opposite a spacebetween a protuberance 31 and a protuberance 32. One side of eachprotuberance; 33 is sub After the interwinding of element 11 about allof the jig protuberances, a second end portion 37 is bent around theother half of the outermost part of the protuberance 33 containing theslot 34, and inserted into the slot 34 adjacentthe first end portion 36.The two end portions- 36 and 37 of element 11 should fit tightly withinthe slot 34 to thereby anchor the ends of element 11 with respect to thejig 26.

A ring element 38 preferably composed of the same metal as jig 26 isshown in Fig. 6 in concentric relationship with the jig. The thicknessof element 38 along its axis is equal to the thickness of jig section 23along the axis II. An upper inner section 39 of ring element 33 has aninner diameter which is larger than the diameter of jig section 23 by anamount which is slightly greater than the thickness of element 11. Alower inner section 41 of element 38 is chamfered. This is shown moreclearly in Figs. 7 and 8.

The annular grid supporting member 16 is also shown in Fig. 6 inconcentric relationship with jig 26 above element 38. Member 16 iscomposed of a metal having a temperature coefiicient of expansionslightly lower than the temperature coefficient of expansion of jig 26.

senses?- The inner surface of member 16 is plated with suitable brazingmaterial for bonding member 16 to the outer portions 13 of the gridelement 11. The inner diameter of member 16 is of the same order ofmagnitude as the inner diameter of section 39 of ring element 38.

The ring element 38 is first located in relation to the jig 26 at theposition shown in Fig. 7, the cham fered section 41 thereof facilitatingthe placing of element 38 down over the end of the jig 26 so that partof section 39 of element 38 forces the outer portions of grid element 11inward toward the outermost end parts of the jig protuberances 33. Theannular member 16 is then placed on top of element 38 as shown in Fig. 7so that part of this member also engages the outer portions of element11. The member 16 and element 38 are then pushed downward until thebottom of element 38 abuts the annular jig seat 29 and the bottom ofmember 42 rests upon the top of element 38 at the locations shown inFig. 8. The outermost portions of grid element 11 outward of jigprotuberances 33 are, therefore, maintained in compression toward theend parts of the protuberances 33 by the annular grid supporting member16.

The parts shown in Fig. 6, after being assembled as shown in Fig. 8, arethen placed in an oven and heated in a hydrogen atmosphere to atemperature above the melting point of the brazing material on the innersurface of member 16. During the heating the jig 26 expands rapidlyoutward of its axis. The outward expansion of jig 26 from its axiscauses element 11 to be tightened about the jig protuberances 31, 32 and33 because of the fact that element 11 has a much lower temperaturecoefi'icient of expansion and its ends are anchored in the slot 34 of ajig protuberance 33. Thus, the outer portions 13 of element 11 are heatbent and conformed to the outermost end parts of the jig protuberances33 and the apexes of the V-shaped sections of element 11 are heat-bentand conformed to the innermost ends of protuberances 31 and 32.

If the inner diameter of member 16 is properly chosen relative to thediameter of jig section 28, the thickness of element 11, and thedifference in expansion of jig 26 and member 16 because of theirdilferent temperature coefiicients, the portions 13 of element 11 becomefirmly compressed against the inner plated surface of member 16 duringthe heating. This occurs because the member 16 has a slightly lowertemperature coefiicien-t of expansion than jig 26. Therefore, since theassembly is heated to a temperature above the melting point of thebrazing material plated to the inner surface of member 16, the outersurfaces of the portions 13 of element 11 can become rigidly bonded tothe inner surface of member 16.

After heating the assembly for a sufiicient time at the propertemperature, the jig 26, ring element 38 and annular member 16 areremoved from the oven and allowed to cool. The jig 26 contracts andelement 11 becomes firmly afiixed to member 16 upon hardening of thebrazing material. After cooling, the grid assembly can be readilyremoved from the jig 26.

In one particular type of grid which has been made by the aforedescribedprocess to have a configuration as shown in Fig. 1, the grid element 11is composed of tungsten. The supporting'member 16 for such a grid iscomposed of a nickel-copper alloy containing 63 to 70 percent nickel.Copper brazing material is employed for bonding or fixing the innersurface of member 16 to portions 13 of grid element 11. The copper hasbeen plated to the inner surface of member 16 before the grid assemblingand brazing steps, for example.

The assembly comprising jig 26 and element 38 utilized to form grids ofthe particular materials described above. is composed. of a highchromium stainless steel type No. 302 as described on pages 3-l9 ofKents Mechanical Engineers Handbook, 11th ed., Design Shop Practice.This type steel is desirable because it has a much higher temperaturecoefficient of expansion than that of tungsten. Furthermore, thesurfaces of an assembly of such material become oxidized during theheating process so that the grid element 11 and annular grid supportingmember 16 will not become bonded to the steel by the copper brazingmaterial. Suflicient oxidation occurs, even in a hydrogen gaseousatmosphere, because of an inherent content of moisture therein. Ifdesired, moisture can be added to the gaseous atmosphere to increasethis oxidation during the heating of the jig.

To form a grid utilizing the particular materials described above theassembly such as is shown in Fig. 8 should be heated in the ovencontaining the hydrogen atmosphere for six to eight minutes at atemperature between 1120-1140 degrees centigrade. It has been founddesirable to place a 'weight or weights of some sort on top of the jig26 and interwound element 11 to insure that element 11 does not buckleupward during the heating. After heating, the aforedescribed assembly isremoved from the oven for cooling. After cooling the aforementionedweight or weights are removed and the grid is ready to be taken from thejig.

A grid having .l-shaped sections 17 as shown in Fig. 2 can bemanufactured by first forming a grid as shown in Fig. 1 by theaforedescribed process. Then, the V- shaped sections 12 and 14 aresuitably out or sheared by any suita ble tool to provide the J-shapedsections 17 wherein the longer radial arms of adjacent sections are nextto each other and the shorter radial arms of adjacent sections are nextto each other.

Obviously other cantilever-type grids could also be formed by theaforedescribed process. For example, a pyramid-type grid wherein all ofthe V-shaped sections such as 12 and 14 of Fig. 1 extended inwardly ofthe grid supporting ring by equal distances could be made. This wouldmerely require a jig wherein the innermost ends of all of the inner jigprotuberances such as 31 and 32 in Fig. 6 were contiguous with the samecircle. The apexes of the V-shaped sections of the grid formed therefromcould be cut to form yet another type grid having radial arms extendinginwardly of the grid supporting ring by equal amounts with their innerends free of each other. Furthermore, the apexes of the V-shapedsections could also be cut to form a grid having J-shaped sectionswherein a long arm of each J-shaped section is adjacent the short arm ofan adjacent section.

Referring to Figs. 9 and 10, a jig 46 is shown for manufacturing anarched-vane grid as shown in Fig. 3. The jig 46 is comprised of a bottomcylindrical section 4'), an upper coaxial cylindrical section 48 havinga smaller diameter than section 4 7, a first set of protuberances 49-60, and a set of rod-like protuberances 62 on a flat face 61 of jigsection 48. The jig i6 is composed of a metal having a substantiallyhigher temperature coeflicient of expansion than that of the thinmetallic element 21 of Fig. 3.

The protuberances 49-60 and 6-2 all have the same dimensions along theaxis Iii-11 of jig 46. These protu'berances are shaped and located asshown in the plan view of Fig. 9 so that the dot-dash lines illustratedtherearound and between the protuberances conform generally to theoutline of the configuration formed by the narrow edge of grid element21 of the finished grid shown in Fig. 3.

The parts of protuberances 49-60 farthest from the axis II-II of jig 4-6are conformal with the cylindrical side of the section 48 of jig 46. Thesides of the protuberances 4960 are perpendicular to the jig face 61.

The rod-like protuberances 62 are also perpendicular to the jig face 61.Protuberances 62 are equally spaced along a diameter of the jig face 61and located at the sositions shown in Fig. 9 so that the sections 22 ofthe grid shown in Fig. 3 will attain the proper curvature when formingthe grid.

To provide the grid of Fig. 3, an elongated strip of metal 21 having agreater width than thickness is interwound back and forth across partsof the face 61 of jig 46 from protuberance 49 to protuberance 55,following the general path of the dot-dash lines in Fig. 9. The endportions 23 and 23 of the element 21 shown in Fig. 3 are bent aroundends of protuberances 49 and 55, respectively, to provide suitableanchorage.

Once the element 21 is interwound upon the jig 46 as described, theprocess of making permanent heat bends in the grid element and mountingthe element in an annular grid supporting element 24 is undertaken. Thisprocess is identical with that described with reference to Figs. 6-8 soneed not be repeated.

Since changes in the aforedescribed process and grid assemblies ofdifferent configurations and/or different materials than specificallydescribed herein could be made without departing from the scope of thepresent invention, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

What is claimed is:

1. A process of forming a grid for an electron beam tube device,comprising anchoring one end of an elongated strip-like metallic elementupon a jig having an appreciably larger temperature coefiicient ofexpansion than said metallic element, interwinding said element inedgewise relationship with respect to a face of said jig back and forthin the same plane across parts of said jig face from one to another of aplurality of predeterminedly shaped and distributed protuberancesextending from said jig face to thereby provide a substantially planarvane-type grid configuration, anchoring the other end of said elementupon said jig, placing a grid supporting member around said element uponsaid jig in close relationship with portions of said element for bondingbetween said element and said member upon application of heat, heatingthe assembly comprising said jig, said element and supporting member tothereby expand said jig relative to said element and tighten saidelement about said protuberances so that portions of said element areheat-bent to closely conform to parts of the peripheries of saidprotuberances, and cooling said assembly to thereby rigidly bond saidelement to .said member and permanently fix the shapesof the bends insaid element and provide for ready removal of said element from said jigafter contraction thereof.

2. A process of forming a grid for an electron beam tube device,comprising interwinding an elongated metallic strip-like element backand forth in the same plane across parts of the face of a jig from oneto another of a plurality of predeterminedly shaped and distributedprotuberances extending from said jig face and anchoring the ends ofsaid element upon said jig, said jig having an appreciably largertemperature coefiicient of expansion than said metallic element,enveloping said protuberances and interwound element with an annularsupporting member having a slightly lower temperature coefficient ofexpansion than said jig and an inner periphery in close proximity withwide portions of said element around parts of a first group among saidprotuberances, said inner periphery of said supporting member beingsubstantially conformal with said parts of said first group ofprotuberances and separated from said portions of said element by amaterial for uniting said member and element in response to heatingthereof, heating the assemblycomprising said jig, said element and saidsupporting member to thereby expand said jig relative to said elementand supporting member and tighten said element about said protuberances,said wide portions of said element being thereby heat-bent and closelyconformed to said parts of said first group of protuberances and saidinner periphery of said supporting member, and cooling said assembly tothereby permanently fix the shapes of the bends in said element andunites said element to said supporting member to provide for readyremovalof said element and supporting member from said jig aftercontraction thereof.

3. A process of forming a grid for an electron beam tube device,comprising interwinding an elongated metallic strip-like element havinga first temperature coeificient of expansion back and forth in the sameplane across parts of the face of a jig in edgewise relationship withrespect to said face fr m one to another of a plurality ofpredeterminedly shaped and distributed protuberances extending from saidjig face, seating a grid supporting ring member upon said jig around theinterwound element, said ring member having a lower temperatureeoefficient of expansion than said jig with the inner surface of saidring member being plated with a brazing material and in close proximityto wide portions of said element about outermost protuberances furthestfrom the center of said ring member, heating the assembly comprisingsaid jig, the interwound element and the supporting member above amelting point of said brazing material to expand said jig so that saidoutermost peripheral parts of said outermost protuberances are in closerproximity to said ring element and said interwound element is heat-bentabout said protuberances, and cooling the foregoing heated assembly inorder to permanently bond said grid element to said ring member and toenable said grid element and supporting ring member to be removed fromsaid jig so as to provide a rugged vane-type grid suitable for electronbeam tubes.

4. A process of forming a grid, comprising the steps of: anchoring oneend of a thin, elongated metallic strip-like element upon a metallic jighaving a plurality of predeterminedly distributed protuberances from aface of said jig, a group of said protuberances being disposed in aring, said jig having a substantially larger temperature c0- efficientof expansion than said element; drawing said element back and forth inthe same plane in edgewise relationship across parts of the face of saidjig and bending said element about parts of said protuberances to form asubstantially planar vane-type grid configuration generally like apredetermined configuration suitable for a grid in an electron beam tubedevice; anchoring the other end of said element upon said jig; placingan annular grid supporting member in surrounding closely spacedrelationship with said group of said jig protuberances so that portionsof said element are between said group of protuberances and the innersurface of said supporting member, means being provided for brazing saidportions to said member; heating the assembly comprising said jig, saidelement, said supporting member and said brazing means to a temperatureabove the melting point of said brazing means, the heat causing said jigto expand for forcing said portions of said element in closerrelationship with said grid supporting member and said element to becometightened about said protuberances to thereby cause the configuration ofsaid element to more closely conform to said predeterminedconfiguration; and cooling said assembly to rigidify said element andcause said portions to become rigidly bonded to said supporting memberby said brazing means.

References Cited in the file of this patent UNITED STATES PATENTS2,398,609 Werner Apr. 16, 1946 3,654,940 Law Oct. 13, 1953 2,678,486Chick et a1. May 18, 1954 2,738,438 Shepherd Mar. 13, 1956 2,825,839Beck et a1. Mar. 4, 1958

